Cinematographic projection apparatus



Aug. 30, 1932. R. RUHNAU 1,875,193

CINEMATOGRAPHIC PROJECTION APPARATUS Filed Jan. 23, 1931 Patented Aug. 30, 1932 UNITED STATES PATENT OFFICE RICHARD RUHNAU, F ESSEX,- GERMANY, ASSIGNOR TO AGFA ANSCO CORPORATION, 01'

BINGHAMTON, NEW YORK, A CORPORATION OF NEW YORK Application filed January 23, 1981, Serial No.

greater portion of each cycle of operation of the machine and for returning the mirror 1 in the opposite direction during the remainder of the cycle; and the object of this invention is to provide anew coaction of the movements of the picture band and of the oscillations of the mirror.

With cinema projectors having optical compensation of the picture displacement by means of an oscillating mirror, it is known to control this oscillating by a cam element. The cam element is driven positively with the drive of the conveyer drum or sprocket. In

practice, it has been found that such a drive does not produce exact agreement between the movements of the picture band and the respective mirror movements. Moreover, slight differences in the distances between the perforations or damaged perforations cause irregularity of movement of both elements, so that perceptible faults in theprojection result.

According to this invention, these faults are avoided in that the oscillating mirror is controlled by the picture band itself but independently of its perforations. This result is attained in a simple manner by arranging a plain roller between the gate and the. conveyer drum which is actuated by the picture band and controls the oscillating mirror. Y The drawing illustrates one form of, construction of the invention by way of example. In the drawing, Fig. 1 is a perspective view (partly in section) of an apparatus which illustrates one form which my invention may take; Fig. 2 is a front elevation of the apparatusshown in Fig. 1.

In these figures, 10 is a side wall of the projection apparatus carrying the arcuate film guide or gate 1 provided with a picture open- 3 ing 1a. 3 is the conveyer wheel or sprocket mounted on the shaft 7 which has its bearing in the side wall 10. The shaft 7 extends 510,777, and in Germany November 12, 1929.

through the latter and is rotated in any desired manner, for instance, by a manually operated crank 6 or by a motor. The main shaft 7 also carries a gear 8 that meshes with a gear 9 secured to the shaft 12 to which shaft is connected thmm 11 which returns the mirror to normal position at the beginning of .a new cycle of the machine.

4 is a plain roller over the periphery of which the film band 2 running from a supply to a rewind reel, is guided when being moved by the sprocket 3 continuously and uniformly through the arcuate path 1. Counterpressure rollers 5 ensure, on the one hand,.

that when the film band is stationary, it is not raised from the roller and, on the other hand, that the roller 4 is rotated in a regular manner by the moving film band. The plain roller 4 is mounted on the shaft 13 which carries also the friction disc 14, the later being in contact with the friction disc 15 secured to the shaft 16. Both the shafts 13 and 16 have their bearings in the pedestal framing 18, the bearing of shaft 13 .being somewhat elastic. In order to ensure a strong frictional contact between the discs 14 and 15, a spring 17 is provided on the framing 18 pressing the disc 14 towards the disc 15.

' The shaft 16 carried by the shaft pedestals 18 and 19, is provided on one end with a pivot 20 (see Fig. 2) serving as a pin-bearing for the axis 21 of the mirror 28. The other end of the shaft 21 is rotatably mounted in a side wall 10. A spring 23 presses the bead 24 of the shaft 16 provided with a fabric 22 enhancing the friction towards the bead 25 of the shaft 21 carrying the mirror. A lever 26 bearing a pin 27 is secured to the bead 25.

The pin 27 projects into the sphere of action of the cam 11. 29 is a casing for the illuminating device arranged above the picture opening 1a of the film guide 1, and 30 is an objective secured to the side wall of the casing.

to receive the rays of light from the mir- I'OI 28. 1".

The operation of this device is as follows: The sprocket 3 turns at constant speed and moves the picture. band 2 through the gate 1. In the picture field 1a the part of the picture tape just passing it, is illuminated in the known manner by the light rays coming from the lamp casing 29 and the light rays passing the picture field, are reflected by the mirror 28 into the objective 30. The movement of the picture band is compensated by a corresponding oscillation of the mirror 28. In order to compensate shrinkage of the film hand without peculiar adjustment of the oscillations of the mirror, the latter is actuated by the movin picture band itself. This is accomplished y guiding the film band over the plain roller 4 which thus is turned ,in strict accordance with the movement of the film band. The rotation is transferred by the friction disc 14 onto the friction disc 15. In this manner the shaft 16 isturned in the direction indicated in Fig. 1 by an arrow. By the elastic frictional coupling of the shaft 16 with the mirror shaft 21, the latter is turned in the same direction. The diameter of the plain tion discs 14 and 15 are so chosen that the mirror is caused to move through one half the angular distance travelled by the film band during the period it is reflecting. Thus, the movement of the picture band is compensated in the known manner and the light rays reflected to the objective, yield a stationary picture on the projection screen. When the film band has been moved in the picture opening the width of one picture the mirror 28 is to be set back to the beginning position in order to compensate the migrationof the following picture. For this purpose, the cam 11 is provided which is turned by the gear 9. When the mirror 28 has reached the end of its projecting movement, the pin 27 mounted on the lever 26, comes in contact with the cam 11 and turns back the mirror by the action of the rib 11a of the cam opposite to the direction of its frictional drive. As soon as the pin 27 comes free from. the curvature 11a, the mirror 28 again is turned by the shaft 16 rotated by the friction roll 15. By this coaction, the mirror 28 carries out an oscillating movement.

and it is turned in the same direction as the picture band moves, at one half the angular velocity of the picture tape until it is returned by the action of the cam 11a under the coaction of the-pin 27 and the lever 26. The movement of the compensating mirror, being independent of the driving device and controlled by the film band, is such that the movement of the mirror agrees exactly with the movement of the picture band, and thus excellent reproduction is obtained.

What 1 claim is 2- 1. In a cinematographic projector, the combination of an arcuate guide for the per forated film band, a lens, a compensating mirror anda supporting shaft therefor coroller 4 and the diameters of the fricitself, but independently of the perforations of the film, andnieans to turn said shaft in the opposite direction.

2. In a cinematographic combination of an arcuate gui e or the perforated film band, a lens, a. compensating mirror and a supporting shafttherefor coaxial with the axis of the film guide, a plain roller rotatable by the moving film band independently of its perforations, means for transmitting the rotation of said plain roller to the shaft of the mirror, and means to turn said shaft in the opposite direction.

3. In a cinematographic projector, the combination of an arcuate guide for the perforated film band, a lens, a compensating mirror and a supporting shaft therefor coaxial with the axis of the film guide, a lain roller rotatable by the moving film and independently of its perforations, means for transmitting the rotation of said plain roller to the shaft of the mirror and causing the latter to turn at one half the angular velocity of the moving film band, and means to turn said shaft in the opposite direction.

4. In a cinematographic projector, the combination of an arcuate guide for the perforated film band, a lens, a compensating mirror and a supporting shaft therefor'coaxial with the axis of the film guide, a toothed conveyer roller, a plain roller rotatable by the moving film band independently of its perforations, means for transmitting the rotation of said plain roller to the shaft of the mirror, and means positively connected with the conveyer roller to turn said shaft in the opposite direction.

5. In a cinematographic rojector, the combination of an arcuate gui e for the perforated film band, a lens, a compensating mirror and a supporting shaft therefor coaxial with the axis of the film guide, a toothed conveyer roller, a shaft for said roller, a plain roller rotatable bythe moving film band independently of its perforations, a pair of rollers transmitting by friction the rotation of said plain roller to the said cam and said arm causing the mirror to turn in the opposite direction. 7

In testimony whereof, I afiix my signature.

\ RIC i'l RUHNAU.

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